Seeing Previously Invisible Molecules For The First Time

ScienceDaily (Oct. 24, 2009) — A team of Harvard chemists led by X. Sunney Xie has developed a new microscopic technique for seeing, in color, molecules with undetectable fluorescence. The room-temperature technique allows researchers to identify previously unseen molecules in living organisms and offers broad applications in biomedical imaging and research.

Many biologically important colored molecules such as hemoglobin -- an oxygen-transport protein in red blood cells -- absorb light but do not fluoresce. Instead, the electrons in these molecules release their additional but transient energy by converting it to heat.

"Since these molecules do not fluoresce, they have literally been overlooked by modern optical microscopes," Xie said.

To detect non-fluorescent molecules in biological systems, Xie and his team developed a new type of microscopy based on stimulated emission.



Stimulated emission image of the microvascular network in a mouse's ear. The sample shows in red the blood vessel network surrounding green-colored sebaceous glands. Sebaceous glands are microscopic glands located in skin that secrete an oily and waxy matter used to lubricate the skin and hair of animals. A technique called confocal reflectance was simultaneously used to record the green-colored sebaceous glands. The image is based on contrasts of non-fluorescent hemoglobin molecules. In the zoomed-in image, individual red blood cells are lined up within a single capillary approximately five micrometers in diameter. A micrometer is one-millionth of a meter. (Credit: X. Sunney Xie, Department of Chemistry and Chemical Biology, Harvard University)

more:

http://www.sciencedaily.com/releases/2009/10/091023104704.htm

A better description might be that this is another way to localize molecules without tagging them or depending upon autofluorescence.

in the last few years. I think it was anthracene that was imaged in the last few months.